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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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166                                ALASKAN GLACIER STUDIES
the earthquakes shook down avalanches into their reservoirs. Among others we especially suspect that there was an advance of Blossom Island Glacier whose outer, moraine-covered surface was very rough in 1906 and whose front extended far beyond the mountain valley, and of Hendrickson Glacier which had moraine-covered ice resting upon overridden .gravels in 1905, the moraine being entirely free from vegetation. McCarty and Rasmussen Glaciers may also have advanced before 1905.
One of the most spectacular events in the recent glacial history of the Yakutat Bay region was the downfall of one of three small glaciers perched in steeply-sloping valleys on the west side of Disenchantment Bay. These three glaciers were so steeply perched in their hanging valleys as to attract our attention, and we were led to photograph them from the fiord on the 3rd of July, 1905, as had been done in 1890 by Russell, in 1895 by the boundary surveyors, and in 1899 by Gilbert. It happened that this day, July 8, 1906, was the last day in the existence of one of these glaciers, the southermost, which we now call Fallen Glacier. This glacier is estimated to have had a length of approximately a mile, and was supplied chiefly from a steep mountain crest down which the snow slid into a spoon-shaped cirque about halfway down the slope. From this amphitheatre the ice protruded as a crevassed, cascading tongue, the lower end lying at an elevation of about 1000 feet above the fiord, and separated from it by an ice-steepened rock slope. On the 4th of July, the day after we photographed the glacier, the entire glacier mass slid out of its valley and a large part of it tumbled into the fiord. The fall of so much ice into the water started a water wave which rose to a height of 110 feet on the shore just south of the glacier, breaking off alder bushes at that elevation. Three miles to the north, near Turner Glacier, the water wave killed vegetation at an elevation of 55 feet, and a wave swept across the north end of Haenke Island at an elevation of 50 or 60 feet. At that point in one place where it was locally concentrated, the wave washed out good-sized alders at an elevation of 115 feet.
In addition to the breaking off and uprooting of alder bushes, the wave caused much erosion wherever it came into contact with unconsolidated deposits, cutting small cliffs and gullies in the till and alluvial fans. The annual plants were killed up to the elevation which the water wave reached, and in succeeding days it was possible to trace the level to which the wave rose by the zone of parched brown grass and other vegetation killed by the bath in salt water. Small icebergs were left stranded far above high tide in several places, a number being found on the site where our camp had stood on the day before the fall of the glacier. We had fortunately moved our camp a distance of about 15 miles, to a new site in Russell Fiord, where we were separated from the glacier fall by Osier Island, and by the high mountainous point above it.
At the time of the glacier fall we were working along the coast east of our camp and were surprised by the appearance of a series of waves, which at first were ascribed to some unusually large fall of icebergs from Hubbard Glacier; but since the waves increased in height until they finally rose 15 or 20 feet above the water level, and since they were much higher than any previously observed iceberg waves, and lasted much longer, we inferred that they must be the result of an earthquake, until the next day, when one of our native packers, returning from Yakutat, gave us the true explanation of the phenomenon. The native further stated that this was the third time that this glacier had